Automatic electrical precipitator



1945. v. DAHLMAN 2,383,111

AUTOMATIC ELECTRICAL PRECIPITATOR Filed March 18, 1943 5 Sheets-Sheet 1 VM/Vf/ MM INVENTOR.

A TTORNEYS.

1945. v. DAHLMAN 2,383,111

- AUTOMATIC ELECTRICAL PREGIPITATOR Filed March 18, 1943 5 Sheets-Sheet 2 INVENTOR.

BY MW A TTORNEYS.

Aug. 21, 1945. I VLDAHLMAN AUTOMATIC ELECTRICAL PRECIPITATOR Filed March 18, 1945 5 Sheets-Sheet 5 i W mm MAN IN VEN TOR.

Patented Aug. 21,1945

UNITED SI 'ATE S PATENT OFFICE AU'l-OMATIC WATCH Verner Dahlman,

American Air Filter Ky., a corporation of Application March 18, 1943, Serial No. 479,665

13 Claims. .(Cl. lea-"n This invention relates to automatic electrostatic precipitators, i. e., electrical precipitators of the automatic or self-cleaning type disclosed in the Pound-Rush U. 8. Patent #2312385, granted August 27, 1940. Although cleaners this type could be designed for the heavy duty uses of dust arrestors or collectors volumes of air containing process dust, l. e., heavy or dense dust concentrations, for all practical purposes, their design is limited to the light duty uses of ventilating air cleaners volumes of air containing atmospheric dust, i. e., light dust concentrations. Both process and atmospheric dust particles range from extremely small microscopic sizes upwardly but the average size of the process dust particle is, as a rule, much larger than that of the atmospheric dust particle.

The principal object of this invention is to improve automatic electrical precipitators to the end of rendering them easier to construct and less liable to electrical insulation failures.

Another object is to eliminate the necessity of insulating individual precipitating plates with a consequent simplification of the cleaner as a whole which handle largeand a lessening oi the chances of insulation failure. i v

A further object is to provide a novel cell assembly of the plate type. I

The invention mainly resides in the feature 0! mounting all 01 the alternate precipitating plates, 1. e., all plates of one electrical sign, for movement along a path having gas-cleaning and filtercleahing areas and all of the intermediate precipitating plates, 1. e., all plates of the opposite electrical sign, in the gas cleaning area to interleave the alternate plates as they pass through that area. With this arrangement one set of plates may be insulated as a whole from the opposite set of plates, thus eliminating the necessity oi insulating individual plates. Furthermore, since it is easier electrically to insulate stationary parts than his to insulate moving parts, all of the moving plates may be electrically grounded through the conveyor, thus eliminating amr necessity for insulating moving plates and requiring only the insulation of the stationary plates as a whole.

In electrical air cleaners of the'pre-ionizing type wherein an ionizer is placed in advance of the precipitating plate-type electrodes, it is customary to employ positive ionization so that the bulk, of the charged particles, is deposited on thenegative or grounded plates which are called the"cold" plates as distinguished from the positively charged "hot Louisville, Ky, ma nolto Inc, Louisville,

Delaware which handle large are charged with an operating voltage below the "pin point threshold" voltage oi the negative plates;'that is to say the voltage at which, as the operating voltage is gradually raised, pale corona discharges nrst appear in the dark as pin points or light scattered over the negative plates, but particularly along the marginal edges.

\ hence, the operating voltage must belovvered even plates. .Norrnallythe plates more if pinpoint ionization ls to he avoided.

A still iurther oo ect is to provide a novel form of precipitatingp atelwmch not omy facilitates the assembly or the plates into cells, but also substantially decreases; the tendency of pin point ionization to occur along their marginal edges and correspondingly increases their pin point threshold voltage" which necessarily permits the 'useof substantially higher operating voltages than would be permissible otherwise.

An air cleaner embodying the invention is illustrated in the accompanying drawings: a

Figure l is a vertical central section through the cleaner, the'sprocket chains being omitted together with some 01' the "movable plate cells tor the sake of clearness;

Figure 2 is a schematic view of the casing as it appears in Figure 1;

Figure 3 is a section along H oi Figure 2;

Figures 4 and 5 are top plan and side elevational. views 01 corresponding link portions or the conveyor chain; Figure 6 is a section along 6-6 of Figure 5;

Figure 7 is a horizontal sectional view correspending to one taken along line 1-1 of Figure 1 but showing the movable plates in elevation instead of section for the sake of clearness;

Figure 8 is a broken perspective view of a movable plate cell; X

Figure 9 is a perspective view of a single prec'ipitating plate shown during one stage of its manuiacture;

Figure 10 is an elevational viewof the securing edge of a single precipitating plate; and s Figure 11 is a section corresponding to one alternate plates So. a are ,veyor for movement along taken along line I of i 'lg'urel l with the bottom portion-of the cleaner broken off,

7 The cleaner illustrated comprises: a housing preferably composed of sheet metal; an upright conveyor within the housing; an ionizer; and an electrical filter medium or precipitator of the plate-type.

The housing or casing l conventionally in-- to a downstream or rear gas outlet "I. Between the front inlet 3 and rear outlet I, the gas successively passes through the following areas: afront gas-cleaning area 4, a central conveyor area 5; and a rear gas-cleaning area 8. The front and rear limits of the central conveyor area 5 are defined by a pair of vertically-arranged front and rear conveyor guides, in the form of channel irons 8, mounted on each Vertical side wall of the casing l. 4,

The upright conveyor, which occupies the central conveyor area 5 comprises: an upper and a lower shaft 9, rotatably mounted on suitable bearings (not shown) which are rigidly secured to opposite side walls of the housing I; a pair of laterally-spaced suitably-notched sprockets It on each shaft 9; and a pair of vertically-arranged laterally-spaced sprocket chains ll, one on the upper and lower sprockets adjacent each side of the housing. The upstream and downstream, or front and rear, flights of each chain ll respectively lie within the channels of the adjacent front and rear conveyor guides 8.

Each conveyor chain H, as indicated in Figures 4-6, is composed of an endless series of alternate links and a similar series of intermediate Each alternate link includes a pair of laterally spaced straps l2, one of which is extended or flanged upwardly and-then bent over the link to form a lug lid. Each intermediate link similarly includes a pair of straps is, but is secured thereto; lug' lid of the alternate linkscarries a bent rigid handle -likestrap ll which cooperates with the lug to form a fixed eye l5. V

' The' ionizer 16 may be of any suitable form. Since the-ionizer illustrated is of the type described and illustrated in the Pound-Rush U. 8. Patent #2311885, granted August 27, 1940, to which reference may be had for'details of its structure and operation, it should sufiice to say that it includes a grounded assembly of large electrodes l1 and an ,insulated assembly of fine wire electrodes it: The ionizer LIE may be mounted'in the central or conveyor area 5, but is preferably mounted on the outside of the housing I over the gas inlet opening 3.

The electrical filter medium or precipitator conventionally-includes a plurality of verticallyarranged plates l! (1. intermediate plates l9b) which, in the gas cleaning area assume the interleaved spaced-plate relationship, of an thereby form-along and across the medium, a plurality of narrow gas-v passages extending through the medium. (seeFigure '1) In"accordance with the main feature of my invention, the

mounted on'the conflxe'd'paths extending through the gas-cleaning and filter-cleaning areas-while the intermediate plates 19b are electrical air condenser and aaaaui mounted on the housing to extend in a fixed position in each gas-cleaning area where they interleave the fixed paths of the alternate plates and thus interleave the alternate plates themselves as they pass through the the gas-cleaning areas.

In other words, all electrically positive plates are mounted as one assembly and all electrically negative plates as an independent assembly. This is advantageous since it enables all positive plates to be insulated from all negative plates simply by insulating one assembly as a unit from the other assembly and thereby not only avoids the multiplicity of insulating parts normally refrom the negative reduces the labor involved in manufacture and substantially minimizes the possibility of electrical break-downs resulting from insulation failures. Furthermore, since the insulation may be, and preferably is, applied to the stationary assembly, the difllculties attending the insulation of a movable assembly, are avoided.

While all precipitating plates l9 may be of any suitable form, straight fiat-surfaced plates composed of sheet metal are shown and preferred.

,. These plates should be made as thin as is possible fold line to provide made wider than the alternate link so that it can tie-telescopically fitted over and pivotally e., alternate plates Isa and consistent with the required mechanical strength but, with the thinner plates, there is a greater tendency for undesirable pin point ionization to occur between the adjacent edges of oppositely charged plates. by providing the plates with rounded blunt edges but, with progressively thinner plates, this desideratum becomes progressively more diillcult to achieve. In accordance with another feature of my invention the alternate and intermediate plates are each formed by folding a thin sheet of metal horizontally over itself along a vertical a two layer plate and by folding the marginal edges 20 of each layer in wardly between layers (see Fig. 9). This type of plate is mechanically strong when made of extremely thin sheet metal. In addition, its marginal edges are rounded or blunted sufilciently to reduce pin point ionization to insignificant proportions. marginal sections of each plate adjacent opposite comers of its vertical (securing) edge, are cut off to provide securing recesses 2|.

The alternate plates Ha may be mounted on the conveyor, and intermediate plates I9b on the housing, in any suitable manner. Preferably, the alternate and intermediate plates are assembled in groups to form alternate plate and intermediate plate cells respectively. Accordingly, each group of plates is, either alternate or interme- ,diate, are assembled in vertically-arranged, horizontally-spaced relation so vertical edges form opposite vertical gas flow faces and their opposite (top andbottom) horizontal edges form opposite horizontal side faces. The term cell assembly thus designates an assembly of parallel plates ofone electrical sign or the other. With this assembly, the plates define gas passages extending, in width, from one horizontal side face to the other, and, in length, from one vertical gas-flow face to the other. The plate along one gas fiow face only, to the cell framework, the

assembly being open along its other gas flow face and along both of its side faces sufiiciently to permit its being interleaved with and moved sidequired to insulate the positive plates individually plates, but also correspondingly This tendency may be reduced;

Before passing, it'may be noted that that their opposite assain ally, if the ionizer It lower cross bar 22, each of which ,is folded to the cross sectional outline of a right angle tribe omitted but v were placedln the central area I. the front intermediate-plate cells should the arrangement illustrated is Y much to be preferred.

angle, from the vertical base of which is struck a, horizontal securing lip 21 for each plate. The corresponding lips 23 of the upper and lower cross bars 22 are dimenslonedto fit into corresponding upper and lower securing recesses 2| of the corresponding plate. In constructing the cell, the plates are loosely assembled on the lips 23ofthecrossbars22 andthenplacedinajlg which rigidly holds them in the proper spaced relationship while they are spot welded to the lips.

It will be noted that the upper and lower cross bars on the alternate plate cells are arranged with their inclined sides facing outwardly away from each other as indicated in Figures 1 and 8. n the intermediate plate cells these cross bars are reversed so that their inclined sides face in wardly toward each other as indicated on Figwardly out of that area.

ure 1. This is done to facilitate the movement of the alternate plate cells around the sprockets. Each alternate-plate cell structure, which'is of one electrical sign, is. completed by welding, or otherwise rigidly securing, to the upper and lower cross bars, at each end of the cell, a vertical end plate 24a. Each 'verticalend plate 24a carries a pair of upper and lower pins 25 which are placed in the fixed eyes It of the conveyor chains II to mount the cells upon the chains.

In operation an ionizing voltage, of say between l1,00 0- and 13,000-volts, may be applied between the large and small electrodes while a precipitating voltage, or say between 5,000 and 7,000 volts, may be applied between the positively charged intermediate plates Nb and the negatively charged or grounded alternate Plates Ila. The air or gas isdrawn or forced through the housing by a suitable blower (not shown) while the conveyor is moved in the direction indicated, by a suitably controlled drive mechanism (not shown), in accordance with usual practice of about 7 every twelve minutes. As the alternate plates pass upwardly from the oil bath, they interleave the stationary intermediate plates in one gas-cleaning area and remain interleaved until they pass up- After they cross over the top of the housing, they move downwardly through the other gas-cleaning area in which the interleaving action is repeated until they clear this area and reenter the oil bath.

The pitch, of the pins 25 is slightly greater I than the pitch of adjacent eyes It on the vertical flightsof the chains I I, so that the pins will press outwardly against the straps It the eyes. At the turns of the chain the eyes I! move angularly about the sprockets along a path of greater radius than the radius of the pitch line of the chain. As a result, the pitch of the eyes I5 is increased relatively to the pitch of the pins causing the eyes to move outwardly relatively to the pins.

The space between each end of the alternate.

plate cells and the adjacent conveyor guide I is sealed by an angle iron 2t adjustably secured to the conveyor guide I. This angle iron seal 20 is adjustably mounted, for movement toward and away from the cells, so that when the cells are properly positioned, the seal may be moved to and fixed in'a position where it rubs against the end plates 21a. In this way the seals 28 also'coop'erate to guide and maintain the cells in proper position during their travel-- through the gas cleaning areas.

The intermediate-plate cell structure which is of the oppositeelectricalsign, is completed by welding, or otherwise rigidly seeming, to the upper and lower cross bars at each end of the cell, a vertical end plate 24b.- These cells are mounted on, but insulated -from,-the housing by forming The ionizer It electrically charges the dust, smoke, fume and other air-borne particles passing through it while the electrostatic field set up between the interleaved precipitator plates in both gas-cleaning areas tends to efiect the precipitation of the bulk of such particles on,

the plates in the front area and of the -remain-* ing particles on the plates in the rear area. As

-' a result, the removal of the particles from the air stream is efiiciently accomplished. when the plates pass through the oil bath in the platecleaning area, the precipitated particles are subjected to the washing action of the oil which is 40fairly clfective in removing them from the plates.

The reference numeral 29 and the reference numerals 30 and SI respectively denote mecha-' nism for cleaning the stationary and movable Plate assemblies, the details of which are fully I disclosed in my co-pending application Serial Number 489,849.

Having described my invention, I claim:

1. In an electrical gas cleaner: a series of spaced alternate precipitating plates of one electrical sign; means for moving the plates bodily along a path having gas-cleaning and filtar-cleaning areas; a series of spaced intermediate precipitating plates of opposite electrical, sign mounted in the gas-cleaning area to inter- I leave the alternate plates as they pass bodily bolting the end plates 24!) to vertical bars 21,.

the'upper andlowerends ,of which are secured to insulators-20 which are rigidly mounted on the housing. The bolting connection between the end plates 24b and the upright" bars 21 is 'cipitating field in the gas through said area, said interleaved plates cooperating to form gas passages therebetween; and means. for establishing an electrostatic preplates in the gas-cleaning area.

2. In an electrical gas'cleaner: a movable assembly of spaced alternate precipitating plates of one electrical sign arranged to travel bodily along a path having gas-cleaning and filtercleaning areas; a stationary assembly of spaced horizontally adjustable to a slight degree topermit horizontal adjustment in the position of the intermediate cells. It will be'understoodof, course, that one group of intermediate-plate cells is thus mounted in the upstream pass or front gas-cleaning area 4 while "another set of such cells similarly mounted in downstream pass or rear gas-cleaning area i. Naturintermediate precipitating plates of opposite electrical sign mounted in the gas-cleaning area to interleave the alternate plates. as they pass bodily through said area, the interleaved alterhate and intermediate plates cooperating in the gas cleaning area to form as passages therebetween; and means for establishing an electrical precipitating field in the gas passages bepassages between 4 a,sss,111

connected-toground and insulated-from-rg'round 5 respectively. I

4, The arrangement of claim 2 wherein each assembly is composed of one or more cells, each cell including: a framework; a plate assembly, "com.-

posed of a number of spaced plates presenting opposite side edges and opposite gas flow edges respectively the opposite side edges forming opposite side faces and the opposite gas-flow edges forming opposite gas flow faces; and means rigidly securing the plate assembly, along one of its gas flow faces on to the framework, the plate assembly as a whole projecting from the framework and being open along its other gas flow face and its side faces suiliciently to permit its being interleaved with, and moved sidewise relatively to, an opposed plate assembly of opposite electrical sign.

5. In an electrical gas cleaner: a series of alternate and of intermediate precipitating plate cells, each cell being composed of a framework and an assembly of spaced precipitating plates rigidly secured to the framework and projecting outwardly therefrom; means for moving a succession of the alternate cells, which are .of one electricalsign, along a path having gas-cleaning and filter-cleaning areas, the cell framework moving along one side of the gas-cleaning area with thealternate plates moving edgewise through said area; and means stationarily mounting the framework of the intermediate cells, which are of the opposite electrical sign, along the other side of the gas-cleaning area with the intermediate plates projecting into said area in position to interleave the alternate plates as they pass through said area.

6. An electrical gas-cleaning precipitatingplate cell of one electrical sign comprising: a framework; a plate assembly, composed of a number of spaced plates presenting opposite side edges and opposite gas-flow edges respectively, 4

the opposite side edges forming opposite side faces and the opposite gas-flow edges forming gas-flow faces; and means rigidly securing the plate assembly, along one of its gas-flow faces only, to the framework, the assembly being open along its other gas-flow face and its side faces sufliciently to permit its being interleaved with,

and moved sidewise relatively to, the plate assembly of an opposed cell of opposite electrical sign.

7. The cell of claim 6 wherein the framework includes: a cross bar extending crosswise relatively to the plate edges of the adjacent gas-flow face; and a series of rigid securing lips, one for each plate, extending from the bar to the plates and rigidly connected to both.

8. An electrical gas-cleaning precipitatingplate cell of one electrical sign comprising: a pair of horizontally-arranged vertically-spaced cross bars; a number of vertically-arranged horizontally-spaced plates presenting horizontal side edges and vertical gas-flow edges respectively, the opposite side edges forming opposite horizontal side faces and the opposite gas-flow edges forming opposite vertical gas-flow faces, the vertical edge of each plate,-along one gas-flow face, being formed with an upper and 'a lower securing recess; .a series of lips, one extending from within each upper and each lower securing recess respectively to each upper and each lower.

crossbar; and'means rigidly securing each lip to each plate and bar.

9. In an electrical gas cleaner; an upright end- I thereof; an electrical-gas-cleaning precipitating-plate cell having a vertical end plate at each of its opposite ends: and apair of upper and lower pins secured to each end plate in position to extend into corresponding upperand lower eyes of the conveyor to mount the'cell on the conveyor, the pitch of the eyes being not larger along the straight sections of the conveyor, but larger along the curved sections thereof, than the pitch of the pins.

. 10. In an electrical gas cleaner: an upright housing having a horizontal gas passage extending from a gas inlet successively through an upstream gas-cleaning area, a central conveyor area and a downstream gas-cleaning area to a gas outlet; a pair of vertically-arranged conveyor guides mounted on' each side of the housing respectively adjacent the upstream and downstream limits of the conveyor area; an endless upright conveyor, having straight-vertical and curved-end sections, mounted in the conveyor area with its straight- ,vertical sections extending into said conveyor guides; a succession of precipitating cells, each cell having a vertical end plate at each end, mounted on the conveyor; a plate'vertically-arranged between each conveyor 1 guide and the space occupied by the adjacent precipitating cells;

and means-adjustably securing each plate, along 0 one vertical margin, to'the adjacent guide for horizontal adjustment toward and from said cell space, the other vertical-margin of each plate frictionally engaging the endplates of the adjacent cells.

11. In an electrical gas .cleaner having a frame and means on the frame prescribing a path of movement extending through a gas cleaning area: a movable plate assembly composed of a series of spaced parallel plates mounted upon the frame for movement along saidpath with'its plates extending into said path; a relatively stationary plate assembly composed of a similar series of spaced parallel plates mounted on the frame with its plates extending into said path at the gas cleaning area; the plates of one assembly being insulated from the other and of both assemblies being so arranged in said path that they interleave each other and form gas passages therebetween during movement of the movable assembly through the gas cleaning area; means for so moving the movable assembly; andmeans for establishing an electrostatic precipitating field projecting outwardly therefrom in spaced parallel relationship, the spaces formed by the projecting portionsfof the plate elements being open and unobstructed internally between the plates and peripherally along the edges of the plates sumciently to permit a similar assembly .of parallel elements to beunitarily moved into and removed from interleaving relationship in which successive elements of each assembly extend into successive spaces between elements of the other assembly.

13. A cell-like assembly of precipitating plates for electrical gas cleaners comprising: a framework; and an assembly of precipitating plates of one electrical sign secured to said framework and projecting outwardly therefrom in spaced parallel relationship, the spaces formed by the projecting portions of the plate elements being 1 open and unobstructed internally between plates and peripherally along the edges of the plates sufliciently to enable a. similar assembly of spaced parallel precipitating plates of opposite electrical sign to be unitarily moved into and removed from interleaving relationship in which successive plates of each assembly extend into successive spaces between plates of the other assembly, the plates of one assembly cooperating with the plates of the opposite assembly in interleaving l0 relationship to form gas passages therebetween.

VERNER"DAHIMAN. 

